This invention relates particularly to an improvement in magnetron sputtering etching apparatus suitable for cleaning substrate surfaces or other treatments as a pretreatment prior to deposition of films on the substrate surfaces.
Among conventional etching methods, radio-frequency two electrode etching method using flon gas (fluorocarbon gas) is most typical. With this method, films of silicon, aluminium, or the like can be etched with very fine widths of the order of submicrons. This method has greatly contributed to the development of large scale integrated circuits. However, as this etching method tends to contaminate the substrate surfaces, it is not suitable for cleaning processing of substrate surfaces.
Different from the above method, there has been a radio-frequency two electrode sputtering etching method using argon, which has been conveniently used, because there is no risk of substrate surfaces being contaminated. This method is used for removing contaminated layers to clean semiconductor substrate surfaces by sputtering etching the substrate surfaces in order to bring aluminium wiring layers into direct contact with the substrate surfaces, or for cleaning surfaces of lower wiring layers by sputtering etching their surfaces in order to form upper wiring layers on the lower wiring layers in multilayer wiring process.
In this argon sputtering etching of the prior art, however, the acceleration of charged particles is too high and the temperature of the substrates rises too high, sometimes to several hundred degrees (.degree.C.). These parameters would adversely affect the substrate. In this method, moreover, another advantage is that the etching speed is low.
In order to avoid this problem, recently a magnetron sputtering etching apparatus has been widely used, wherein a magnetic field perpendicularly intersecting an electric field directed to a target is produced in the proximity of a surface of the target to enable the etching to proceed at high speeds. FIG. 1 illustrates such an apparatus of the prior art, particularly its electrodes in a schematic front sectional view.
The apparatus shown in FIG. 1 is one example of the electrode arrangement having a lower electrode on which a substrate to be processed is arranged and an upper electrode which serves also as a target to carry out etching and depositing. The upper opposed electrode includes a ground flat target 111 and an electrode body 112 having a recess to form inner cavities 113 therebetween into which cooling water is introduced through cooling water conduits 114 and 115 to cool the target 111, whose temperature is likely to be high. An iron core 117 equipped with magnets 116 is arranged on a rear surface of the target 111 on the side of the electrode body to generate a closed magnetic field 118 in the proximity of opposite surfaces of the two electrodes.
On the other hand, the lower etching electrode includes the substrate 121, a substrate holder 122 and a radio frequency power source 124 connected through a capacitor 123 to the substrate holder 122 and is arranged immediately below the upper opposed electrode.
With this etching apparatus having the electrode arrangements, its etching speed is quite high with the aid of its magnetron system. However, the etching on the surface of the substrate 121 has a distribution corresponding to the configuration of the magnetic field. Therefore, etching on the surface are not uniform so that there are excessively etched and insufficiently etched portions on the surface which would cause local inconductivity in semiconductor circuits.